Accuracy of guided endodontic access evaluated through a fully digital workflow with three-dimensional vector-based measurement: an in vitro study

To characterize a fully digital, vector-based workflow for assessing the accuracy of static guided endodontic access and to determine the precision of access execution under controlled laboratory conditions, minimizing methodological bias associated with tomographic-based measurements. This in vitro experimental study used 18 three-dimensionally printed resin replicas of a standardized maxillary central incisor (tooth #11) model with a flattened apical surface allowing direct visual verification of the access point. Static guided endodontic access was performed by a single calibrated operator using a static guide planned in Implant Studio (3Shape, Copenhagen, Denmark) with a metal sleeve (1.5-mm internal diameter; 7.5-mm length). The dependent variable was the linear deviation (mm) between the planned and executed access centers, obtained by superimposing pre- and post-operative STL meshes in Medit Design software. Intra-operator reliability was assessed according to COSMIN standards (ICC 3,1 , standard error of measurement [SEM], minimal detectable change at 95% confidence [MDC95], and Bland–Altman analysis). The mean linear deviation was 0.260 ± 0.221 mm (95% CI 0.150–0.369 mm; median 0.249 mm). Bland–Altman analysis revealed a bias of 0.004 mm and narrow limits of agreement (− 0.024 to 0.032 mm). Intra-operator reliability was excellent (ICC 3,1 = 0.998; SEM = 0.0101 mm; MDC95 = 0.028 mm). Among the included samples, 88.9% showed a deviation ≤ 0.5 mm, all remained below the 0.7 mm inclusion threshold by definition. The deviation was statistically greater than zero (Wilcoxon signed-rank, p < 0.001), but a sensitivity analysis excluding the two largest observations confirmed the robustness of the findings. Under controlled laboratory conditions, static guided endodontic access demonstrated high accuracy, with deviations predominantly within clinically accepted limits. The proposed fully digital, vector-based workflow proved to be a precise and highly reproducible alternative to tomographic-based measurement methods for assessing procedural accuracy in experimental endodontic research.